/**
 * Copyright 2010 The Apache Software Foundation
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.nutch.util;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.util.Comparator;
import java.util.Iterator;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.io.RawComparator;
import org.apache.hadoop.io.WritableComparator;
import org.apache.hadoop.io.WritableUtils;

/**
 * Utility class that handles byte arrays, conversions to/from other types,
 * comparisons, hash code generation, manufacturing keys for HashMaps or
 * HashSets, etc. Taken from Hbase Utils to avoid a dependency
 */
public class Bytes {

	private static final Logger LOG = LoggerFactory.getLogger(Bytes.class);

	/** When we encode strings, we always specify UTF8 encoding */
	public static final String UTF8_ENCODING = "UTF-8";

	/**
	 * An empty instance.
	 */
	public static final byte[] EMPTY_BYTE_ARRAY = new byte[0];

	/**
	 * Size of boolean in bytes
	 */
	public static final int SIZEOF_BOOLEAN = Byte.SIZE / Byte.SIZE;

	/**
	 * Size of byte in bytes
	 */
	public static final int SIZEOF_BYTE = SIZEOF_BOOLEAN;

	/**
	 * Size of char in bytes
	 */
	public static final int SIZEOF_CHAR = Character.SIZE / Byte.SIZE;

	/**
	 * Size of double in bytes
	 */
	public static final int SIZEOF_DOUBLE = Double.SIZE / Byte.SIZE;

	/**
	 * Size of float in bytes
	 */
	public static final int SIZEOF_FLOAT = Float.SIZE / Byte.SIZE;

	/**
	 * Size of int in bytes
	 */
	public static final int SIZEOF_INT = Integer.SIZE / Byte.SIZE;

	/**
	 * Size of long in bytes
	 */
	public static final int SIZEOF_LONG = Long.SIZE / Byte.SIZE;

	/**
	 * Size of short in bytes
	 */
	public static final int SIZEOF_SHORT = Short.SIZE / Byte.SIZE;

	/**
	 * Estimate of size cost to pay beyond payload in jvm for instance of byte
	 * []. Estimate based on study of jhat and jprofiler numbers.
	 */
	// JHat says BU is 56 bytes.
	// SizeOf which uses java.lang.instrument says 24 bytes. (3 longs?)
	public static final int ESTIMATED_HEAP_TAX = 16;

	/**
	 * Byte array comparator class.
	 */
	public static class ByteArrayComparator implements RawComparator<byte[]> {
		/**
		 * Constructor
		 */
		public ByteArrayComparator() {
			super();
		}

		public int compare(byte[] left, byte[] right) {
			return compareTo(left, right);
		}

		public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2,
				int l2) {
			return compareTo(b1, s1, l1, b2, s2, l2);
		}
	}

	/**
	 * Pass this to TreeMaps where byte [] are keys.
	 */
	public static Comparator<byte[]> BYTES_COMPARATOR = new ByteArrayComparator();

	/**
	 * Use comparing byte arrays, byte-by-byte
	 */
	public static RawComparator<byte[]> BYTES_RAWCOMPARATOR = new ByteArrayComparator();

	/**
	 * Read byte-array written with a WritableableUtils.vint prefix.
	 * 
	 * @param in
	 *            Input to read from.
	 * @return byte array read off <code>in</code>
	 * @throws IOException
	 *             e
	 */
	public static byte[] readByteArray(final DataInput in) throws IOException {
		int len = WritableUtils.readVInt(in);
		if (len < 0) {
			throw new NegativeArraySizeException(Integer.toString(len));
		}
		byte[] result = new byte[len];
		in.readFully(result, 0, len);
		return result;
	}

	/**
	 * Read byte-array written with a WritableableUtils.vint prefix. IOException
	 * is converted to a RuntimeException.
	 * 
	 * @param in
	 *            Input to read from.
	 * @return byte array read off <code>in</code>
	 */
	public static byte[] readByteArrayThrowsRuntime(final DataInput in) {
		try {
			return readByteArray(in);
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * Write byte-array with a WritableableUtils.vint prefix.
	 * 
	 * @param out
	 *            output stream to be written to
	 * @param b
	 *            array to write
	 * @throws IOException
	 *             e
	 */
	public static void writeByteArray(final DataOutput out, final byte[] b)
			throws IOException {
		if (b == null) {
			WritableUtils.writeVInt(out, 0);
		} else {
			writeByteArray(out, b, 0, b.length);
		}
	}

	/**
	 * Write byte-array to out with a vint length prefix.
	 * 
	 * @param out
	 *            output stream
	 * @param b
	 *            array
	 * @param offset
	 *            offset into array
	 * @param length
	 *            length past offset
	 * @throws IOException
	 *             e
	 */
	public static void writeByteArray(final DataOutput out, final byte[] b,
			final int offset, final int length) throws IOException {
		WritableUtils.writeVInt(out, length);
		out.write(b, offset, length);
	}

	/**
	 * Write byte-array from src to tgt with a vint length prefix.
	 * 
	 * @param tgt
	 *            target array
	 * @param tgtOffset
	 *            offset into target array
	 * @param src
	 *            source array
	 * @param srcOffset
	 *            source offset
	 * @param srcLength
	 *            source length
	 * @return New offset in src array.
	 */
	public static int writeByteArray(final byte[] tgt, final int tgtOffset,
			final byte[] src, final int srcOffset, final int srcLength) {
		byte[] vint = vintToBytes(srcLength);
		System.arraycopy(vint, 0, tgt, tgtOffset, vint.length);
		int offset = tgtOffset + vint.length;
		System.arraycopy(src, srcOffset, tgt, offset, srcLength);
		return offset + srcLength;
	}

	/**
	 * Put bytes at the specified byte array position.
	 * 
	 * @param tgtBytes
	 *            the byte array
	 * @param tgtOffset
	 *            position in the array
	 * @param srcBytes
	 *            array to write out
	 * @param srcOffset
	 *            source offset
	 * @param srcLength
	 *            source length
	 * @return incremented offset
	 */
	public static int putBytes(byte[] tgtBytes, int tgtOffset, byte[] srcBytes,
			int srcOffset, int srcLength) {
		System.arraycopy(srcBytes, srcOffset, tgtBytes, tgtOffset, srcLength);
		return tgtOffset + srcLength;
	}

	/**
	 * Write a single byte out to the specified byte array position.
	 * 
	 * @param bytes
	 *            the byte array
	 * @param offset
	 *            position in the array
	 * @param b
	 *            byte to write out
	 * @return incremented offset
	 */
	public static int putByte(byte[] bytes, int offset, byte b) {
		bytes[offset] = b;
		return offset + 1;
	}

	/**
	 * Returns a new byte array, copied from the passed ByteBuffer.
	 * 
	 * @param bb
	 *            A ByteBuffer
	 * @return the byte array
	 */
	public static byte[] toBytes(ByteBuffer bb) {
		int length = bb.remaining();
		byte[] result = new byte[length];
		System.arraycopy(bb.array(), bb.arrayOffset() + bb.position(), result,
				0, length);
		return result;
	}

	/**
	 * This method will convert utf8 encoded bytes into a string. If an
	 * UnsupportedEncodingException occurs, this method will eat it and return
	 * null instead.
	 * 
	 * @param bb
	 *            Presumed UTF-8 encoded ByteBuffer.
	 * @return String made from <code>b</code> or null
	 */
	public static String toString(ByteBuffer bb) {
		return bb == null ? null
				: toString(bb.array(), bb.arrayOffset() + bb.position(),
						bb.remaining());
	}

	/**
	 * @param b
	 *            Presumed UTF-8 encoded byte array.
	 * @return String made from <code>b</code>
	 */
	public static String toString(final byte[] b) {
		if (b == null) {
			return null;
		}
		return toString(b, 0, b.length);
	}

	/**
	 * Joins two byte arrays together using a separator.
	 * 
	 * @param b1
	 *            The first byte array.
	 * @param sep
	 *            The separator to use.
	 * @param b2
	 *            The second byte array.
	 */
	public static String toString(final byte[] b1, String sep,
			final byte[] b2) {
		return toString(b1, 0, b1.length) + sep + toString(b2, 0, b2.length);
	}

	/**
	 * This method will convert utf8 encoded bytes into a string. If an
	 * UnsupportedEncodingException occurs, this method will eat it and return
	 * null instead.
	 * 
	 * @param b
	 *            Presumed UTF-8 encoded byte array.
	 * @param off
	 *            offset into array
	 * @param len
	 *            length of utf-8 sequence
	 * @return String made from <code>b</code> or null
	 */
	public static String toString(final byte[] b, int off, int len) {
		if (b == null) {
			return null;
		}
		if (len == 0) {
			return "";
		}
		try {
			return new String(b, off, len, UTF8_ENCODING);
		} catch (UnsupportedEncodingException e) {
			LOG.error("UTF-8 not supported?", e);
			return null;
		}
	}

	/**
	 * Write a printable representation of a ByteBuffer. Non-printable
	 * characters are hex escaped in the format \\x%02X, eg: \x00 \x05 etc
	 * 
	 * @param bb
	 *            ByteBuffer to write out
	 * @return string output
	 */
	public static String toStringBinary(ByteBuffer bb) {
		return bb == null ? null
				: toStringBinary(bb.array(), bb.arrayOffset() + bb.position(),
						bb.remaining());
	}

	/**
	 * Write a printable representation of a byte array.
	 * 
	 * @param b
	 *            byte array
	 * @return string
	 * @see #toStringBinary(byte[], int, int)
	 */
	public static String toStringBinary(final byte[] b) {
		return toStringBinary(b, 0, b.length);
	}

	/**
	 * Write a printable representation of a byte array. Non-printable
	 * characters are hex escaped in the format \\x%02X, eg: \x00 \x05 etc
	 * 
	 * @param b
	 *            array to write out
	 * @param off
	 *            offset to start at
	 * @param len
	 *            length to write
	 * @return string output
	 */
	public static String toStringBinary(final byte[] b, int off, int len) {
		StringBuilder result = new StringBuilder();
		try {
			String first = new String(b, off, len, "ISO-8859-1");
			for (int i = 0; i < first.length(); ++i) {
				int ch = first.charAt(i) & 0xFF;
				if ((ch >= '0' && ch <= '9') || (ch >= 'A' && ch <= 'Z')
						|| (ch >= 'a' && ch <= 'z')
						|| " `~!@#$%^&*()-_=+[]{}\\|;:'\",.<>/?"
								.indexOf(ch) >= 0) {
					result.append(first.charAt(i));
				} else {
					result.append(String.format("\\x%02X", ch));
				}
			}
		} catch (UnsupportedEncodingException e) {
			LOG.error("ISO-8859-1 not supported?", e);
		}
		return result.toString();
	}

	private static boolean isHexDigit(char c) {
		return (c >= 'A' && c <= 'F') || (c >= '0' && c <= '9');
	}

	/**
	 * Takes a ASCII digit in the range A-F0-9 and returns the corresponding
	 * integer/ordinal value.
	 * 
	 * @param ch
	 *            The hex digit.
	 * @return The converted hex value as a byte.
	 */
	public static byte toBinaryFromHex(byte ch) {
		if (ch >= 'A' && ch <= 'F')
			return (byte) ((byte) 10 + (byte) (ch - 'A'));
		// else
		return (byte) (ch - '0');
	}

	public static byte[] toBytesBinary(String in) {
		// this may be bigger than we need, but lets be safe.
		byte[] b = new byte[in.length()];
		int size = 0;
		for (int i = 0; i < in.length(); ++i) {
			char ch = in.charAt(i);
			if (ch == '\\') {
				// begin hex escape:
				char next = in.charAt(i + 1);
				if (next != 'x') {
					// invalid escape sequence, ignore this one.
					b[size++] = (byte) ch;
					continue;
				}
				// ok, take next 2 hex digits.
				char hd1 = in.charAt(i + 2);
				char hd2 = in.charAt(i + 3);

				// they need to be A-F0-9:
				if (!isHexDigit(hd1) || !isHexDigit(hd2)) {
					// bogus escape code, ignore:
					continue;
				}
				// turn hex ASCII digit -> number
				byte d = (byte) ((toBinaryFromHex((byte) hd1) << 4)
						+ toBinaryFromHex((byte) hd2));

				b[size++] = d;
				i += 3; // skip 3
			} else {
				b[size++] = (byte) ch;
			}
		}
		// resize:
		byte[] b2 = new byte[size];
		System.arraycopy(b, 0, b2, 0, size);
		return b2;
	}

	/**
	 * Converts a string to a UTF-8 byte array.
	 * 
	 * @param s
	 *            string
	 * @return the byte array
	 */
	public static byte[] toBytes(String s) {
		try {
			return s.getBytes(UTF8_ENCODING);
		} catch (UnsupportedEncodingException e) {
			LOG.error("UTF-8 not supported?", e);
			return null;
		}
	}

	/**
	 * Convert a boolean to a byte array. True becomes -1 and false becomes 0.
	 * 
	 * @param b
	 *            value
	 * @return <code>b</code> encoded in a byte array.
	 */
	public static byte[] toBytes(final boolean b) {
		return new byte[] { b ? (byte) -1 : (byte) 0 };
	}

	/**
	 * Reverses {@link #toBytes(boolean)}
	 * 
	 * @param b
	 *            array
	 * @return True or false.
	 */
	public static boolean toBoolean(final byte[] b) {
		if (b.length != 1) {
			throw new IllegalArgumentException(
					"Array has wrong size: " + b.length);
		}
		return b[0] != (byte) 0;
	}

	/**
	 * Convert a long value to a byte array using big-endian.
	 * 
	 * @param val
	 *            value to convert
	 * @return the byte array
	 */
	public static byte[] toBytes(long val) {
		byte[] b = new byte[8];
		for (int i = 7; i > 0; i--) {
			b[i] = (byte) val;
			val >>>= 8;
		}
		b[0] = (byte) val;
		return b;
	}

	/**
	 * Converts a byte array to a long value. Reverses {@link #toBytes(long)}
	 * 
	 * @param bytes
	 *            array
	 * @return the long value
	 */
	public static long toLong(byte[] bytes) {
		return toLong(bytes, 0, SIZEOF_LONG);
	}

	/**
	 * Converts a byte array to a long value. Assumes there will be
	 * {@link #SIZEOF_LONG} bytes available.
	 * 
	 * @param bytes
	 *            bytes
	 * @param offset
	 *            offset
	 * @return the long value
	 */
	public static long toLong(byte[] bytes, int offset) {
		return toLong(bytes, offset, SIZEOF_LONG);
	}

	/**
	 * Converts a byte array to a long value.
	 * 
	 * @param bytes
	 *            array of bytes
	 * @param offset
	 *            offset into array
	 * @param length
	 *            length of data (must be {@link #SIZEOF_LONG})
	 * @return the long value
	 * @throws IllegalArgumentException
	 *             if length is not {@link #SIZEOF_LONG} or if there's not
	 *             enough room in the array at the offset indicated.
	 */
	public static long toLong(byte[] bytes, int offset, final int length) {
		if (length != SIZEOF_LONG || offset + length > bytes.length) {
			throw explainWrongLengthOrOffset(bytes, offset, length,
					SIZEOF_LONG);
		}
		long l = 0;
		for (int i = offset; i < offset + length; i++) {
			l <<= 8;
			l ^= bytes[i] & 0xFF;
		}
		return l;
	}

	private static IllegalArgumentException explainWrongLengthOrOffset(
			final byte[] bytes, final int offset, final int length,
			final int expectedLength) {
		String reason;
		if (length != expectedLength) {
			reason = "Wrong length: " + length + ", expected " + expectedLength;
		} else {
			reason = "offset (" + offset + ") + length (" + length
					+ ") exceed the" + " capacity of the array: "
					+ bytes.length;
		}
		return new IllegalArgumentException(reason);
	}

	/**
	 * Put a long value out to the specified byte array position.
	 * 
	 * @param bytes
	 *            the byte array
	 * @param offset
	 *            position in the array
	 * @param val
	 *            long to write out
	 * @return incremented offset
	 * @throws IllegalArgumentException
	 *             if the byte array given doesn't have enough room at the
	 *             offset specified.
	 */
	public static int putLong(byte[] bytes, int offset, long val) {
		if (bytes.length - offset < SIZEOF_LONG) {
			throw new IllegalArgumentException(
					"Not enough room to put a long at" + " offset " + offset
							+ " in a " + bytes.length + " byte array");
		}
		for (int i = offset + 7; i > offset; i--) {
			bytes[i] = (byte) val;
			val >>>= 8;
		}
		bytes[offset] = (byte) val;
		return offset + SIZEOF_LONG;
	}

	/**
	 * Presumes float encoded as IEEE 754 floating-point "single format"
	 * 
	 * @param bytes
	 *            byte array
	 * @return Float made from passed byte array.
	 */
	public static float toFloat(byte[] bytes) {
		return toFloat(bytes, 0);
	}

	/**
	 * Presumes float encoded as IEEE 754 floating-point "single format"
	 * 
	 * @param bytes
	 *            array to convert
	 * @param offset
	 *            offset into array
	 * @return Float made from passed byte array.
	 */
	public static float toFloat(byte[] bytes, int offset) {
		return Float.intBitsToFloat(toInt(bytes, offset, SIZEOF_INT));
	}

	/**
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset to write to
	 * @param f
	 *            float value
	 * @return New offset in <code>bytes</code>
	 */
	public static int putFloat(byte[] bytes, int offset, float f) {
		return putInt(bytes, offset, Float.floatToRawIntBits(f));
	}

	/**
	 * @param f
	 *            float value
	 * @return the float represented as byte []
	 */
	public static byte[] toBytes(final float f) {
		// Encode it as int
		return Bytes.toBytes(Float.floatToRawIntBits(f));
	}

	/**
	 * @param bytes
	 *            byte array
	 * @return Return double made from passed bytes.
	 */
	public static double toDouble(final byte[] bytes) {
		return toDouble(bytes, 0);
	}

	/**
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset where double is
	 * @return Return double made from passed bytes.
	 */
	public static double toDouble(final byte[] bytes, final int offset) {
		return Double.longBitsToDouble(toLong(bytes, offset, SIZEOF_LONG));
	}

	/**
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset to write to
	 * @param d
	 *            value
	 * @return New offset into array <code>bytes</code>
	 */
	public static int putDouble(byte[] bytes, int offset, double d) {
		return putLong(bytes, offset, Double.doubleToLongBits(d));
	}

	/**
	 * Serialize a double as the IEEE 754 double format output. The resultant
	 * array will be 8 bytes long.
	 * 
	 * @param d
	 *            value
	 * @return the double represented as byte []
	 */
	public static byte[] toBytes(final double d) {
		// Encode it as a long
		return Bytes.toBytes(Double.doubleToRawLongBits(d));
	}

	/**
	 * Convert an int value to a byte array
	 * 
	 * @param val
	 *            value
	 * @return the byte array
	 */
	public static byte[] toBytes(int val) {
		byte[] b = new byte[4];
		for (int i = 3; i > 0; i--) {
			b[i] = (byte) val;
			val >>>= 8;
		}
		b[0] = (byte) val;
		return b;
	}

	/**
	 * Converts a byte array to an int value
	 * 
	 * @param bytes
	 *            byte array
	 * @return the int value
	 */
	public static int toInt(byte[] bytes) {
		return toInt(bytes, 0, SIZEOF_INT);
	}

	/**
	 * Converts a byte array to an int value
	 * 
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset into array
	 * @return the int value
	 */
	public static int toInt(byte[] bytes, int offset) {
		return toInt(bytes, offset, SIZEOF_INT);
	}

	/**
	 * Converts a byte array to an int value
	 * 
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset into array
	 * @param length
	 *            length of int (has to be {@link #SIZEOF_INT})
	 * @return the int value
	 * @throws IllegalArgumentException
	 *             if length is not {@link #SIZEOF_INT} or if there's not enough
	 *             room in the array at the offset indicated.
	 */
	public static int toInt(byte[] bytes, int offset, final int length) {
		if (length != SIZEOF_INT || offset + length > bytes.length) {
			throw explainWrongLengthOrOffset(bytes, offset, length, SIZEOF_INT);
		}
		int n = 0;
		for (int i = offset; i < (offset + length); i++) {
			n <<= 8;
			n ^= bytes[i] & 0xFF;
		}
		return n;
	}

	/**
	 * Put an int value out to the specified byte array position.
	 * 
	 * @param bytes
	 *            the byte array
	 * @param offset
	 *            position in the array
	 * @param val
	 *            int to write out
	 * @return incremented offset
	 * @throws IllegalArgumentException
	 *             if the byte array given doesn't have enough room at the
	 *             offset specified.
	 */
	public static int putInt(byte[] bytes, int offset, int val) {
		if (bytes.length - offset < SIZEOF_INT) {
			throw new IllegalArgumentException(
					"Not enough room to put an int at" + " offset " + offset
							+ " in a " + bytes.length + " byte array");
		}
		for (int i = offset + 3; i > offset; i--) {
			bytes[i] = (byte) val;
			val >>>= 8;
		}
		bytes[offset] = (byte) val;
		return offset + SIZEOF_INT;
	}

	/**
	 * Convert a short value to a byte array of {@link #SIZEOF_SHORT} bytes
	 * long.
	 * 
	 * @param val
	 *            value
	 * @return the byte array
	 */
	public static byte[] toBytes(short val) {
		byte[] b = new byte[SIZEOF_SHORT];
		b[1] = (byte) val;
		val >>= 8;
		b[0] = (byte) val;
		return b;
	}

	/**
	 * Converts a byte array to a short value
	 * 
	 * @param bytes
	 *            byte array
	 * @return the short value
	 */
	public static short toShort(byte[] bytes) {
		return toShort(bytes, 0, SIZEOF_SHORT);
	}

	/**
	 * Converts a byte array to a short value
	 * 
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset into array
	 * @return the short value
	 */
	public static short toShort(byte[] bytes, int offset) {
		return toShort(bytes, offset, SIZEOF_SHORT);
	}

	/**
	 * Converts a byte array to a short value
	 * 
	 * @param bytes
	 *            byte array
	 * @param offset
	 *            offset into array
	 * @param length
	 *            length, has to be {@link #SIZEOF_SHORT}
	 * @return the short value
	 * @throws IllegalArgumentException
	 *             if length is not {@link #SIZEOF_SHORT} or if there's not
	 *             enough room in the array at the offset indicated.
	 */
	public static short toShort(byte[] bytes, int offset, final int length) {
		if (length != SIZEOF_SHORT || offset + length > bytes.length) {
			throw explainWrongLengthOrOffset(bytes, offset, length,
					SIZEOF_SHORT);
		}
		short n = 0;
		n ^= bytes[offset] & 0xFF;
		n <<= 8;
		n ^= bytes[offset + 1] & 0xFF;
		return n;
	}

	/**
	 * Put a short value out to the specified byte array position.
	 * 
	 * @param bytes
	 *            the byte array
	 * @param offset
	 *            position in the array
	 * @param val
	 *            short to write out
	 * @return incremented offset
	 * @throws IllegalArgumentException
	 *             if the byte array given doesn't have enough room at the
	 *             offset specified.
	 */
	public static int putShort(byte[] bytes, int offset, short val) {
		if (bytes.length - offset < SIZEOF_SHORT) {
			throw new IllegalArgumentException(
					"Not enough room to put a short at" + " offset " + offset
							+ " in a " + bytes.length + " byte array");
		}
		bytes[offset + 1] = (byte) val;
		val >>= 8;
		bytes[offset] = (byte) val;
		return offset + SIZEOF_SHORT;
	}

	/**
	 * @param vint
	 *            Integer to make a vint of.
	 * @return Vint as bytes array.
	 */
	public static byte[] vintToBytes(final long vint) {
		long i = vint;
		int size = WritableUtils.getVIntSize(i);
		byte[] result = new byte[size];
		int offset = 0;
		if (i >= -112 && i <= 127) {
			result[offset] = (byte) i;
			return result;
		}

		int len = -112;
		if (i < 0) {
			i ^= -1L; // take one's complement'
			len = -120;
		}

		long tmp = i;
		while (tmp != 0) {
			tmp = tmp >> 8;
			len--;
		}

		result[offset++] = (byte) len;

		len = (len < -120) ? -(len + 120) : -(len + 112);

		for (int idx = len; idx != 0; idx--) {
			int shiftbits = (idx - 1) * 8;
			long mask = 0xFFL << shiftbits;
			result[offset++] = (byte) ((i & mask) >> shiftbits);
		}
		return result;
	}

	/**
	 * @param buffer
	 *            buffer to convert
	 * @return vint bytes as an integer.
	 */
	public static long bytesToVint(final byte[] buffer) {
		int offset = 0;
		byte firstByte = buffer[offset++];
		int len = WritableUtils.decodeVIntSize(firstByte);
		if (len == 1) {
			return firstByte;
		}
		long i = 0;
		for (int idx = 0; idx < len - 1; idx++) {
			byte b = buffer[offset++];
			i = i << 8;
			i = i | (b & 0xFF);
		}
		return (WritableUtils.isNegativeVInt(firstByte) ? ~i : i);
	}

	/**
	 * Reads a zero-compressed encoded long from input stream and returns it.
	 * 
	 * @param buffer
	 *            Binary array
	 * @param offset
	 *            Offset into array at which vint begins.
	 * @throws java.io.IOException
	 *             e
	 * @return deserialized long from stream.
	 */
	public static long readVLong(final byte[] buffer, final int offset)
			throws IOException {
		byte firstByte = buffer[offset];
		int len = WritableUtils.decodeVIntSize(firstByte);
		if (len == 1) {
			return firstByte;
		}
		long i = 0;
		for (int idx = 0; idx < len - 1; idx++) {
			byte b = buffer[offset + 1 + idx];
			i = i << 8;
			i = i | (b & 0xFF);
		}
		return (WritableUtils.isNegativeVInt(firstByte) ? ~i : i);
	}

	/**
	 * @param left
	 *            left operand
	 * @param right
	 *            right operand
	 * @return 0 if equal, < 0 if left is less than right, etc.
	 */
	public static int compareTo(final byte[] left, final byte[] right) {
		return compareTo(left, 0, left.length, right, 0, right.length);
	}

	/**
	 * Lexographically compare two arrays.
	 * 
	 * @param buffer1
	 *            left operand
	 * @param buffer2
	 *            right operand
	 * @param offset1
	 *            Where to start comparing in the left buffer
	 * @param offset2
	 *            Where to start comparing in the right buffer
	 * @param length1
	 *            How much to compare from the left buffer
	 * @param length2
	 *            How much to compare from the right buffer
	 * @return 0 if equal, < 0 if left is less than right, etc.
	 */
	public static int compareTo(byte[] buffer1, int offset1, int length1,
			byte[] buffer2, int offset2, int length2) {
		// Bring WritableComparator code local
		int end1 = offset1 + length1;
		int end2 = offset2 + length2;
		for (int i = offset1, j = offset2; i < end1 && j < end2; i++, j++) {
			int a = (buffer1[i] & 0xff);
			int b = (buffer2[j] & 0xff);
			if (a != b) {
				return a - b;
			}
		}
		return length1 - length2;
	}

	/**
	 * @param left
	 *            left operand
	 * @param right
	 *            right operand
	 * @return True if equal
	 */
	public static boolean equals(final byte[] left, final byte[] right) {
		// Could use Arrays.equals?
		// noinspection SimplifiableConditionalExpression
		if (left == null && right == null) {
			return true;
		}
		return (left == null || right == null || (left.length != right.length)
				? false
				: compareTo(left, right) == 0);
	}

	/**
	 * Return true if the byte array on the right is a prefix of the byte array
	 * on the left.
	 */
	public static boolean startsWith(byte[] bytes, byte[] prefix) {
		return bytes != null && prefix != null && bytes.length >= prefix.length
				&& compareTo(bytes, 0, prefix.length, prefix, 0,
						prefix.length) == 0;
	}

	/**
	 * @param b
	 *            bytes to hash
	 * @return Runs {@link WritableComparator#hashBytes(byte[], int)} on the
	 *         passed in array. This method is what
	 *         {@link org.apache.hadoop.io.Text} and
	 *         {@link ImmutableBytesWritable} use calculating hash code.
	 */
	public static int hashCode(final byte[] b) {
		return hashCode(b, b.length);
	}

	/**
	 * @param b
	 *            value
	 * @param length
	 *            length of the value
	 * @return Runs {@link WritableComparator#hashBytes(byte[], int)} on the
	 *         passed in array. This method is what
	 *         {@link org.apache.hadoop.io.Text} and
	 *         {@link ImmutableBytesWritable} use calculating hash code.
	 */
	public static int hashCode(final byte[] b, final int length) {
		return WritableComparator.hashBytes(b, length);
	}

	/**
	 * @param b
	 *            bytes to hash
	 * @return A hash of <code>b</code> as an Integer that can be used as key in
	 *         Maps.
	 */
	public static Integer mapKey(final byte[] b) {
		return hashCode(b);
	}

	/**
	 * @param b
	 *            bytes to hash
	 * @param length
	 *            length to hash
	 * @return A hash of <code>b</code> as an Integer that can be used as key in
	 *         Maps.
	 */
	public static Integer mapKey(final byte[] b, final int length) {
		return hashCode(b, length);
	}

	/**
	 * @param a
	 *            lower half
	 * @param b
	 *            upper half
	 * @return New array that has a in lower half and b in upper half.
	 */
	public static byte[] add(final byte[] a, final byte[] b) {
		return add(a, b, EMPTY_BYTE_ARRAY);
	}

	/**
	 * @param a
	 *            first third
	 * @param b
	 *            second third
	 * @param c
	 *            third third
	 * @return New array made from a, b and c
	 */
	public static byte[] add(final byte[] a, final byte[] b, final byte[] c) {
		byte[] result = new byte[a.length + b.length + c.length];
		System.arraycopy(a, 0, result, 0, a.length);
		System.arraycopy(b, 0, result, a.length, b.length);
		System.arraycopy(c, 0, result, a.length + b.length, c.length);
		return result;
	}

	/**
	 * @param a
	 *            array
	 * @param length
	 *            amount of bytes to grab
	 * @return First <code>length</code> bytes from <code>a</code>
	 */
	public static byte[] head(final byte[] a, final int length) {
		if (a.length < length) {
			return null;
		}
		byte[] result = new byte[length];
		System.arraycopy(a, 0, result, 0, length);
		return result;
	}

	/**
	 * @param a
	 *            array
	 * @param length
	 *            amount of bytes to snarf
	 * @return Last <code>length</code> bytes from <code>a</code>
	 */
	public static byte[] tail(final byte[] a, final int length) {
		if (a.length < length) {
			return null;
		}
		byte[] result = new byte[length];
		System.arraycopy(a, a.length - length, result, 0, length);
		return result;
	}

	/**
	 * @param a
	 *            array
	 * @param length
	 *            new array size
	 * @return Value in <code>a</code> plus <code>length</code> prepended 0
	 *         bytes
	 */
	public static byte[] padHead(final byte[] a, final int length) {
		byte[] padding = new byte[length];
		for (int i = 0; i < length; i++) {
			padding[i] = 0;
		}
		return add(padding, a);
	}

	/**
	 * @param a
	 *            array
	 * @param length
	 *            new array size
	 * @return Value in <code>a</code> plus <code>length</code> appended 0 bytes
	 */
	public static byte[] padTail(final byte[] a, final int length) {
		byte[] padding = new byte[length];
		for (int i = 0; i < length; i++) {
			padding[i] = 0;
		}
		return add(a, padding);
	}

	/**
	 * Split passed range. Expensive operation relatively. Uses BigInteger math.
	 * Useful splitting ranges for MapReduce jobs.
	 * 
	 * @param a
	 *            Beginning of range
	 * @param b
	 *            End of range
	 * @param num
	 *            Number of times to split range. Pass 1 if you want to split
	 *            the range in two; i.e. one split.
	 * @return Array of dividing values
	 */
	public static byte[][] split(final byte[] a, final byte[] b,
			final int num) {
		byte[][] ret = new byte[num + 2][];
		int i = 0;
		Iterable<byte[]> iter = iterateOnSplits(a, b, num);
		if (iter == null)
			return null;
		for (byte[] elem : iter) {
			ret[i++] = elem;
		}
		return ret;
	}

	/**
	 * Iterate over keys within the passed inclusive range.
	 */
	public static Iterable<byte[]> iterateOnSplits(final byte[] a,
			final byte[] b, final int num) {
		byte[] aPadded;
		byte[] bPadded;
		if (a.length < b.length) {
			aPadded = padTail(a, b.length - a.length);
			bPadded = b;
		} else if (b.length < a.length) {
			aPadded = a;
			bPadded = padTail(b, a.length - b.length);
		} else {
			aPadded = a;
			bPadded = b;
		}
		if (compareTo(aPadded, bPadded) >= 0) {
			throw new IllegalArgumentException("b <= a");
		}
		if (num <= 0) {
			throw new IllegalArgumentException("num cannot be < 0");
		}
		byte[] prependHeader = { 1, 0 };
		final BigInteger startBI = new BigInteger(add(prependHeader, aPadded));
		final BigInteger stopBI = new BigInteger(add(prependHeader, bPadded));
		final BigInteger diffBI = stopBI.subtract(startBI);
		final BigInteger splitsBI = BigInteger.valueOf(num + 1);
		if (diffBI.compareTo(splitsBI) < 0) {
			return null;
		}
		final BigInteger intervalBI;
		try {
			intervalBI = diffBI.divide(splitsBI);
		} catch (Exception e) {
			LOG.error("Exception caught during division", e);
			return null;
		}

		final Iterator<byte[]> iterator = new Iterator<byte[]>() {
			private int i = -1;

			@Override
			public boolean hasNext() {
				return i < num + 1;
			}

			@Override
			public byte[] next() {
				i++;
				if (i == 0)
					return a;
				if (i == num + 1)
					return b;

				BigInteger curBI = startBI
						.add(intervalBI.multiply(BigInteger.valueOf(i)));
				byte[] padded = curBI.toByteArray();
				if (padded[1] == 0)
					padded = tail(padded, padded.length - 2);
				else
					padded = tail(padded, padded.length - 1);
				return padded;
			}

			@Override
			public void remove() {
				throw new UnsupportedOperationException();
			}

		};

		return new Iterable<byte[]>() {
			@Override
			public Iterator<byte[]> iterator() {
				return iterator;
			}
		};
	}

	/**
	 * @param t
	 *            operands
	 * @return Array of byte arrays made from passed array of Text
	 */
	public static byte[][] toByteArrays(final String[] t) {
		byte[][] result = new byte[t.length][];
		for (int i = 0; i < t.length; i++) {
			result[i] = Bytes.toBytes(t[i]);
		}
		return result;
	}

	/**
	 * @param column
	 *            operand
	 * @return A byte array of a byte array where first and only entry is
	 *         <code>column</code>
	 */
	public static byte[][] toByteArrays(final String column) {
		return toByteArrays(toBytes(column));
	}

	/**
	 * @param column
	 *            operand
	 * @return A byte array of a byte array where first and only entry is
	 *         <code>column</code>
	 */
	public static byte[][] toByteArrays(final byte[] column) {
		byte[][] result = new byte[1][];
		result[0] = column;
		return result;
	}

	/**
	 * Binary search for keys in indexes.
	 * 
	 * @param arr
	 *            array of byte arrays to search for
	 * @param key
	 *            the key you want to find
	 * @param offset
	 *            the offset in the key you want to find
	 * @param length
	 *            the length of the key
	 * @param comparator
	 *            a comparator to compare.
	 * @return index of key
	 */
	public static int binarySearch(byte[][] arr, byte[] key, int offset,
			int length, RawComparator<byte[]> comparator) {
		int low = 0;
		int high = arr.length - 1;

		while (low <= high) {
			int mid = (low + high) >>> 1;
			// we have to compare in this order, because the comparator order
			// has special logic when the 'left side' is a special key.
			int cmp = comparator.compare(key, offset, length, arr[mid], 0,
					arr[mid].length);
			// key lives above the midpoint
			if (cmp > 0)
				low = mid + 1;
			// key lives below the midpoint
			else if (cmp < 0)
				high = mid - 1;
			// BAM. how often does this really happen?
			else
				return mid;
		}
		return -(low + 1);
	}

	/**
	 * Bytewise binary increment/deincrement of long contained in byte array on
	 * given amount.
	 * 
	 * @param value
	 *            - array of bytes containing long (length <= SIZEOF_LONG)
	 * @param amount
	 *            value will be incremented on (deincremented if negative)
	 * @return array of bytes containing incremented long (length ==
	 *         SIZEOF_LONG)
	 * @throws IOException
	 *             - if value.length > SIZEOF_LONG
	 */
	public static byte[] incrementBytes(byte[] value, long amount)
			throws IOException {
		byte[] val = value;
		if (val.length < SIZEOF_LONG) {
			// Hopefully this doesn't happen too often.
			byte[] newvalue;
			if (val[0] < 0) {
				newvalue = new byte[] { -1, -1, -1, -1, -1, -1, -1, -1 };
			} else {
				newvalue = new byte[SIZEOF_LONG];
			}
			System.arraycopy(val, 0, newvalue, newvalue.length - val.length,
					val.length);
			val = newvalue;
		} else if (val.length > SIZEOF_LONG) {
			throw new IllegalArgumentException(
					"Increment Bytes - value too big: " + val.length);
		}
		if (amount == 0)
			return val;
		if (val[0] < 0) {
			return binaryIncrementNeg(val, amount);
		}
		return binaryIncrementPos(val, amount);
	}

	/* increment/deincrement for positive value */
	private static byte[] binaryIncrementPos(byte[] value, long amount) {
		long amo = amount;
		int sign = 1;
		if (amount < 0) {
			amo = -amount;
			sign = -1;
		}
		for (int i = 0; i < value.length; i++) {
			int cur = ((int) amo % 256) * sign;
			amo = (amo >> 8);
			int val = value[value.length - i - 1] & 0x0ff;
			int total = val + cur;
			if (total > 255) {
				amo += sign;
				total %= 256;
			} else if (total < 0) {
				amo -= sign;
			}
			value[value.length - i - 1] = (byte) total;
			if (amo == 0)
				return value;
		}
		return value;
	}

	/* increment/deincrement for negative value */
	private static byte[] binaryIncrementNeg(byte[] value, long amount) {
		long amo = amount;
		int sign = 1;
		if (amount < 0) {
			amo = -amount;
			sign = -1;
		}
		for (int i = 0; i < value.length; i++) {
			int cur = ((int) amo % 256) * sign;
			amo = (amo >> 8);
			int val = ((~value[value.length - i - 1]) & 0x0ff) + 1;
			int total = cur - val;
			if (total >= 0) {
				amo += sign;
			} else if (total < -256) {
				amo -= sign;
				total %= 256;
			}
			value[value.length - i - 1] = (byte) total;
			if (amo == 0)
				return value;
		}
		return value;
	}

}
